Configuring Gamma Correction in Linux using xgamma

You can easily change the gamma correction factor in Linux by using the following command

xgamma -gamma newValue

The newValue signifies the new gamma correction factor. It should be around 0.5 - 1. You can use higher or lower values than 0.5-1, but you may end up with much too bright or much too dark screen (the minimum value which the script accepts is 0.1 and the maximum value is 10 - I wouldn't recommend trying those).

The best way to find the ideal gamma value for your monitor is to query first the xgamma value:

xgamma

After querying the value, increase the factor with 0.1 if you want your screen brighter or decrease it with 0.1 if you want your screen darker. Do it until you get the value you seek.

If you want to a fine tunning you can modify the red, green or blue component:

xgamma -rgamma rVal -ggamma gVal -bgamma bVal

The testing method should remain the same as the one described above. Increasing/Decreasing the values too much can leave with an interesting (as in not so great) view.

Useful links:
xgamma man